Both versions are already starting to show up on Ebay, at inflated prices. I'm sure the prices will drop after they've been out awhile. The Seven20 model has a wood-grained look to it, and looks a bit slimmer, at least to my eyes.

Just got the new sonic today. Nice light and sound effects all throughout the casing. While there's a primary "on" button like all previous sonics, there's also a secondary on button that causes the emitter crystal to rotate with a different sound effect than the primary one. My only complaint is that it seems a little delicate in the sense that one has to take special care not to accidentally drop it onto a hard floor or it might damage the electronics, but otherwise I love it.